Jump to content


Photo
- - - - -

End Burner Formulas / Home made motors


  • Please log in to reply
12 replies to this topic

#1 nordicwolf

nordicwolf

    Playing with fire

  • Full Member
  • PipPip
  • 10 posts

Posted 13 January 2022 - 07:19 PM

Hello...For a variety of reasons I want to try making some end burner motors and would like to ask about formulas people have used here successfully.

 

I used to launch Estes rockets years ago and now think it might be fun to try to make some motors that might fly a rocket similar to Estes models. 

 

I have 4 ounce end burner tooling and a bunch of 1/2" ID tubes.  The tubes are 5" long but I figure I can cut them shorter as needed.

 

Questions

1.  what is a good BP formula for a 4oz end burner motor?

2.  What is a good formula for the delay?

3.  what is a good formula for the ejection charge?

4.  What is a good model rocket to try with home made motors?

 

I need to look at the various pyro suppliers, but I am just looking for something simple into which to try home made motors.  A basic tube for a body, basic fins (plastic even) and nosecone.  Mounting the motor might be a bit tricky, but with a 3/4" body, maybe the 4oz motors can friction fit inside the tube if I wrap some masking tape on the motors to fatten them up a bit.

 

I think it might be fun (and less suspicious) to try a home made end burner in an actual rocket instead of taping it to a stick.

 

Thank you for any suggestions.  



#2 MadMat

MadMat

    Pyrotechnician

  • Donator - HE
  • PipPipPipPip
  • 812 posts
  • Gender:Male
  • Location:North-east MO
  • Interests:Anything scientific.

Posted 14 January 2022 - 12:10 AM

Answers: 1. 75/15/10 BP will work fine for an end burner. 2. Add sodium bicarbonate to your BP for delay. Start by adding a couple % and experiment until you have slowed the burn speed to what you want.  3. The fastest burning 75/15/10 BP you can make granulated properly will work for the ejection charge. You want the ejection charge contained, but not packed tight like your grain. 4. I have no idea. You should probably experiment with your motors until you have everything dialed in and then think about a model.


Edited by MadMat, 14 January 2022 - 12:13 AM.


#3 jacket

jacket

    Smelt the smoke

  • Full Member
  • Pip
  • 2 posts

Posted 14 January 2022 - 11:20 AM

To answer question 4. If you have a Hobby Lobby nearby, they sell kits that are relatively inexpensive. I bought my kids a set for Christmas that had 2 rockets, the stand, and the launch controller, for 20 bucks. I'm actually going down a similar road as well. I took out the engine blocks and modified them slightly to hold any size engine you'd like to stuff into them. The actually rocket body is pretty wide on one of them so it makes it relatively easy.

#4 Mumbles

Mumbles

    Grandmaster

  • Admin
  • PipPipPipPipPipPipPipPipPipPip
  • 11,784 posts
  • Gender:Male
  • Location:Above You

Posted 19 January 2022 - 11:40 AM

I think a member here was doing similar things.  Looking for some of his posts might give some ideas or help with this project.  I believe his name was "Bourbon". 

 

One piece of advice I'd give is to try the motors out on their own first.  They can be secured upside down.  You'd probably at least want to confirm they're not going to blow up regularly before using even a cheap model rocket kit.  It'll help to give you an idea of the burn time and delay time to get something in the ballpark of what you want.  They're not too conspicuous on the ground.  It basically will just look like a fountain or something. 


Just so you guys quit asking, here is the link to the old forum. http://www.xsorbit2....forum/index.cgi

The sky is my canvas, and I have 2,113 pounds of powdered paint in the workshop.

#5 Bourbon

Bourbon

    Pyrotechnician

  • Full Member
  • PipPipPipPip
  • 245 posts
  • Gender:Male
  • Location:Oregon
  • Interests:1# BP Stingers right now.

Posted 19 January 2022 - 12:38 PM

Sorry Mumbles, not me. I've never built an end burner. I do know that "Shark" said he has spent years flying rocket kits with different types of BP, and sugar motors with great success. I could be mistaken, but I think he said everything from end burner, nozzled and nozzleless. I think "Justvisiting" was also pressing motors with the intent of making an equal to Estas.



#6 Arthur

Arthur

    Firebreather

  • HE Qualified
  • PipPipPipPipPip
  • 3,602 posts

Posted 19 January 2022 - 12:40 PM

The convenience of an Estes motor is that (because of history) things just fit. Motor tubes fit motors, motors fit rocket bodies etc. Manufacturers tend to make kits for rockets to fit Estes motors.



#7 Mumbles

Mumbles

    Grandmaster

  • Admin
  • PipPipPipPipPipPipPipPipPipPip
  • 11,784 posts
  • Gender:Male
  • Location:Above You

Posted 19 January 2022 - 02:45 PM

I'll see if I can find who I'm thinking of.  Sorry I was mistaken.


Just so you guys quit asking, here is the link to the old forum. http://www.xsorbit2....forum/index.cgi

The sky is my canvas, and I have 2,113 pounds of powdered paint in the workshop.

#8 nordicwolf

nordicwolf

    Playing with fire

  • Full Member
  • PipPip
  • 10 posts

Posted 19 January 2022 - 10:41 PM

Thanks everyone for the responses.

 

Someone told me to use commercial airfloat in the 75:15:10 if I run into CATOs with nozzled core burners.  

That is part of the reason I want to try end burners, hopefully reducing likelihood of catos anyway.

 

I have ERC charcoal and no airfloat, so that is what I will be trying.

 

I know Estes products just fit.  I am not so much interested in making Estes-compatible motors but rather make end burners to put into home made tubes / rockets and see if I can get those to fly.  So I will need propulsion, delay and ejection.  I read that core-burners have too much impulse power that could knock the fins off a model, and end burners (like Estes) have a slower lift off.  So maybe core-burners are for fireworks whereas end burners are more for model rockets (but also used for fireworks I guess.)



#9 Bourbon

Bourbon

    Pyrotechnician

  • Full Member
  • PipPipPipPip
  • 245 posts
  • Gender:Male
  • Location:Oregon
  • Interests:1# BP Stingers right now.

Posted 20 January 2022 - 10:16 AM

Hey, nothing wrong with that. If 75/15/10 is too hot, just keep stepping it down. I'd make small batches of BP first for different combinations, before you make sizable amount for you perfected motors. I bet you find everything you need, in two of the four below.

 

75/15/10

70/20/10

65/25/10

60/30/10

 

Other folks change up the ratios more then I do when dialing in. Or, they keep good track of ratios and math by adding C to the mix to tone it down. I keep it pretty simple with the four above, and, I keep all four around at all times. I even have a couple 100 grams of 55/35/10 laying around for L..O..N..G delay. That's pushing though, in my opinion.


Edited by Bourbon, 20 January 2022 - 10:18 AM.


#10 justvisiting

justvisiting

    Pyrotechnician

  • Full Member
  • PipPipPipPip
  • 412 posts

Posted 20 January 2022 - 11:56 AM

Estes motors achieve the performance and storage ability they do because the propellant grain is very dense. They use high pressing force and the propellant is dampened. When I made end burners for testing, I could only get a density of 1.4g/cc. with dry powder, but with dampened powder I could get 1.8g/cc. That's the density Estes gets. Of course, you'll need a tube support and a press to approach the impulse Estes motors have. The water allows for the use of less pressing force, and a cheap tube support can be made from a strip of mylar .005" thick, snugly wrapped on the tube. 



#11 SharkWhisperer

SharkWhisperer

    Pyrotechnician

  • Donator
  • PipPipPipPip
  • 849 posts
  • Gender:Male

Posted Yesterday, 12:42 AM

Sorry Mumbles, not me. I've never built an end burner. I do know that "Shark" said he has spent years flying rocket kits with different types of BP, and sugar motors with great success. I could be mistaken, but I think he said everything from end burner, nozzled and nozzleless. I think "Justvisiting" was also pressing motors with the intent of making an equal to Estas.

OP Wolf hey there,

 

Have launched a bunch of hybrid Estes-like rockets driven by homemade BP motors. There's a lot of info in prior threads. One amigo, member "HCB" put some videos on Youtube. His first launch of an Estes Patriot Missile used a homemade 1/2" ID motor that outperformed the C-impulse motors that Estes recommends. That video is at: .  It's pretty cool. I had to pay him a whopping $1 for losing a bet that his first rocket would be doing cartwheels or CATO. It didn't--actually it was close to a textbook flight with perfect parachute ejection and recovery. He was getting a 3+ second burn on a long C-sized endburner that took his (likely overweight) rocket to 740 feet at around 140 mph, with G-forces over 15, I believe. He used homemade tooling for 1/2" x 5" motors. You could get it moving faster on a coreburner motor configuration, but you'd want to reinforce your fins (through-the-wall construction, aircraft plywood or balsa/basswood layered, thick filets) and strengthen your motor mount to take the higher G-forces. Personally, I like the long slow burn of an endburner or semi-coreburner in finned rockets.

 

The initial exchanges with HCB and several APC members here on the forum can be found in the following thread and other threads from around that time: https://www.amateurp...tes#entry185018 .  Most exchanges were around Feb-March 2020. There are other threads related to delay/ejection charges from around the same time that might be useful. Some discussions (delays, ejection...) might have been taken offline.

 

You can also do a forum search for "Estes" etc., that should give you some ideas and expectations.

 

All of my BP motors have been hand-rammed to date. Many prefer to press and you will get higher densities with a press, but my motors work pretty well with standard tooling and a 3-pound deadblow hammer. Nozzled end- and coreburners; sometimes short cores (similar to Estes D motors). Usually 1-pounders (3/4" ID), and occasionally 3-pounders, but large BP motors have heavy tubes and a ton of BP in them--at a certain point it just makes sense to switch to lighter AP-based composite propellants. I haven't done any nozzleless motors, though others here do so routinely. Just search "nozzleless".

 

As Bourbon mentioned, Justvisiting is another member with a long history of experimentation on similar subjects. And several other individuals here at APC, too. Ned Gorski wrote a piece about re-creating Estes BP motors that you can find on the Skylighter website: https://www.skylight...-rocket-engines . However, please do not waste your time using the crappy hardwood airfloat charcoal that he did (and that Skylighter sells in their overpriced low-quality "BP" kits).

 

Flying hybrid finned rockets on homemade motors is a blast! Very rewarding. And way cheaper than motors from Estes or Aerotech, especially the larger ones (not counting labor). Commercial BP motors just went up in price at the New Year by about 15-20%, so there's that.

 

Good luck!


  • Bourbon likes this

#12 nordicwolf

nordicwolf

    Playing with fire

  • Full Member
  • PipPip
  • 10 posts

Posted Yesterday, 01:42 AM

Thanks all for the advice and inspiration!

 

Seems trite, but I am totally grateful for the research done and shared here.  Thanks again!


Edited by nordicwolf, Yesterday, 01:44 AM.


#13 Mumbles

Mumbles

    Grandmaster

  • Admin
  • PipPipPipPipPipPipPipPipPipPip
  • 11,784 posts
  • Gender:Male
  • Location:Above You

Posted Yesterday, 11:29 AM

HCB was the member I was thinking of.  Thanks for posting the right person SharkWhisperer.


Just so you guys quit asking, here is the link to the old forum. http://www.xsorbit2....forum/index.cgi

The sky is my canvas, and I have 2,113 pounds of powdered paint in the workshop.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users